It all started in 1967, when construction began on Magic Kingdom. Walt Disney passed away right before they began to build, but he was still a major part in everything they did. Walt had great ideas for the new and improved Disney World. My favorite is they build Magic Kingdom over tunnels called utilidors, so cast members or VIP guests could move through the park without guests seeing them. Also, since Florida has high water, Magic Kingdom is built on a second story, making the utilidors the first story. The elevation of Magic Kingdom is 107ft.
Some more interesting history of Magic Kingdom is that in February of 2011, Mickey's Toontown Fair was closed to make way for a new expansion of Fantasyland. This was a shock to a lot of people. In 2012, a part of the new Fantasyland was reopened and called the Storybook Circus. Dumbo the Flying Elephant was relocated to there and The Barnstomer was renamed to The Great Goofini. The most important history fact to remember; Disneyland is "The Happiest Place On Earth" and Magic Kingdom is "The Most Magical Place On Earth".